Java Reflection Generic Parameter getGenericParameterType(Type type, int index)

Description

get Generic Parameter Type

License

Apache License

Declaration

public static Type getGenericParameterType(Type type, int index) 

Method Source Code

//package com.java2s;
/*//  ww  w.j av a 2 s  .c  o  m
 * Copyright 2014-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

import java.lang.reflect.GenericArrayType;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

public class Main {
    protected static final Type[] EMPTY_TYPES = new Type[0];

    public static Type getGenericParameterType(Type type, int index) {
        if (!ParameterizedType.class.isInstance(type)) {
            return null;
        }
        final Type[] genericParameterTypeList = getGenericParameterTypes(type);
        if (genericParameterTypeList.length == 0
                || genericParameterTypeList.length < index) {
            return null;
        }
        return genericParameterTypeList[index];
    }

    public static Type[] getGenericParameterTypes(Type type) {
        if (ParameterizedType.class.isInstance(type)) {
            final ParameterizedType paramType = ParameterizedType.class
                    .cast(type);
            return paramType.getActualTypeArguments();
        }
        if (GenericArrayType.class.isInstance(type)) {
            final GenericArrayType arrayType = GenericArrayType.class
                    .cast(type);
            return getGenericParameterTypes(arrayType
                    .getGenericComponentType());
        }
        return EMPTY_TYPES;
    }
}

Related

1. getGenericParameter(final Type type)
2. getGenericParameter(final Type type, final int index)
3. getGenericParameterList(Type type)
4. getGenericParameters(final Type type)
5. getGenericParameterType(Method method, int paramIdx)
6. getGenericParameterTypes(final Type type)
7. getGenericParameterTypes(Method m)
8. getGenericParameterTypes(Type t)
9. getGenericParamType(Type type)